Naturespeak

February 1, 2014

An Audacious Arachnid

Filed under: Uncategorized — wykes @ 2:10 pm

On the really really cold days, he snuggles deep within his silken snuggie bag. He peeps out from the folds, like a dog watching traffic through parted window curtains, whenever the thermometer rises into the teens. On days soaring into the 20’s and 30’s he will come out completely and walk about the immediate framework of his shelter. So goes the winter life of my resident jumping spider living in my back porch (the very same un-heated, un-finished back porch featured in my last post).

All teary eyed Charlotte’s Web readers know that many spiders package their next generation as silk-encased eggs and die before the onset of winter. Some spiders do overwinter as adults, however, and my porch mate is a prime example of this tactic. To say that this hairy little dude is hibernating would be a miscarriage of the word. Technically cold-blooded arthropods don’t hibernate – they enter diapause. Because my little charge is a male, I suppose you could call his a state of menopause but that term has already been taken (why is it, by the way, women go through MENapause -shouldn’t it be FEM or WOMANapause?). At any rate, diapause implies a “pausing” of activity but, based on my observations, this is anything but the truth. They are quite active throughout the season.

The spider in question is a Phidippus audax, otherwise known as the Bold Jumping Spider. In case you are wondering, the Latin species name audax literally means “audacious”, or bold if you will. Apart from actually being bold, these spiders are identifiable by their iridescent green chelicera (jaws), hairy black bodies, and orange-spotted backs. The males, averaging 10mm in length, are smaller than the females and possess two tiny horns, or tufts, above their main eyes. Thus the reason I am calling my spider a guy. If he comes out on Super Bowl Sunday then I’ll be positive of this.

The chosen wintering spot for this bold little beast is a woven two-layered silk bag built within an open square of a metal cooking grid. This item functions a spacer for a small aluminum camp kettle during the summer, but the grid dimensions make it a perfect site for Phidippus in the fall and winter. Bold Jumping spiders use their audacious silk producing skills to construct chamber nests for various purposes. Females weave protective bags for eggs; growing individuals construct them for skin-shedding periods, and wintering adults construct them as Arctic sleeping bags. Several rows down and over from the wintering spot, a shed skin indicates that another – perhaps the same guy – used this square as a shedding chamber earlier in the fall (see below).

As I stated earlier, the only time I found this spider completely “paused” was during those hard freeze weeks when the temperatures crashed into the single digits and below. At any other time he was up and out and very alert. It became a challenge to photograph this fellow because he would spot me and retreat whenever I entered the room. I had to sneak upon him as carefully as if it were stalking a wild turkey. I frequently had to resort to my telephoto options!

Jumping spiders have excellent vision. Like most spiders they have four pairs of eyes. The central pair is huge and gives the critters a Jeep-like appearance. Apparently these main eyes are used for primary vision and the extra eyes (including a set on the back of the “head”) for light/dark indications. Thanks to painstaking research it has been determined that Jumpers see most of the world as a fuzzy out-of-focus green place. They do not have binocular vision. Instead, according to Takashi Nagata, of the Osaka City University, they have a four layered retina. The first layer creates a sharp image and the deeper layers register different intensities of UV and green light. The close items become blurry and thus allow for a comparative view for distance judging within each single eye.

Based on this analysis I often appeared as a scary blurry green object in the face of my saltatorial friend. After seeing what this would actually look like in his eyes (see here), I have resolved not to attempt to sneak up on my winter spider for the remainder of the season lest I drive him into a deep diapause from which he may never escape.

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